I. Field
The present disclosure relates generally to communication transceivers, and more specifically, to a receiver front end for use in carrier aggregation communication systems.
II. Background
In a radio frequency (RF) transceiver, a communication signal is developed, upconverted, amplified and transmitted by a transmitter and is received, amplified, downconverted and recovered by a receiver. In the receiver, the communication signal is typically received and downconverted by receive circuitry to recover the information contained in the communication signal. A single transmitter or receiver can be configured to operate using multiple transmit frequencies and/or multiple receive frequencies. For a receiver to be able to simultaneously receive two or more receive signals, the concurrent operation of two or more receive paths is used. Such systems are sometimes referred to as “carrier-aggregation” (CA) systems. The term “carrier-aggregation” may refer to systems that include inter-band carrier aggregation (Inter-CA) and intra-band carrier aggregation (Intra-CA). Inter-CA refers to the processing of two or more separate (either contiguous or non-contiguous) carrier signals that occur in different communication bands. Intra-CA refers to the processing of two or more separate (either contiguous or non-contiguous) carrier signals that occur in the same communication band. A received carrier aggregated RF signal is typically amplified and down-converted using one or more distinct local oscillator (LO) frequencies. The downconverted signals are then processed to extract the information transmitted using the multiple carriers.
Communication devices have RF transceivers that are becoming more and more complex as they are designed to handle an ever-increasing number of different frequencies in multiple communication bands. It is common for a communication device to be able to communicate over a variety of different frequencies over many different communication bands. In many cases, the receiver includes multiple signal paths that give rise to stringent path-to-path isolation requirements because each receiver signal path could generate aggressor signals to other receiver signal paths. When an internal aggressor signal is present on a victim receiver path, a large amount of receiver desensitization can occur due to circuit nonlinearities and/or other external interferers. This makes recovery of the information on the victim receiver path difficult or impossible.
It is therefore desirable to have way to provide improved receiver path isolation when receiving multiple carrier signals in a carrier aggregation transceiver.